1. Technical Challenges:
   • Equipment failures or breakdowns. This can be due to wrong process design parameters or incompatible material of construction selection.
   • Difficulty in maintaining consistent production quality. Possibly process designer has designed a inefficient unit operation, like smaller surface area of the exchanger, wrong selection of pump, insufficient stages in distillation column or limitation of heat management in reactor for the given reaction.
   • Technological upgrades or integration of new systems. This happens when we have selected a older version of control system while particular equipment local control is advance. In such cases it is very difficult to integrate or upgradation.
2. Supply Chain Issues:
   • Delays in material delivery. If we have selected a vendor who is too much loaded or has poor infrastructure we can face delivery issues and delay in project completion. Apart from this if we don’t have a well thought procurement planning then also we are going to face delivery challenges.
   • Fluctuations in raw material costs. In project we plan everything and try to maintain the cost within capex cost. Sometimes steel, cement or chemical cost escalates which will impact heavily the projected capex cost. This can delay the further investments and impacts plant start up.
   • Supply chain disruptions due to external factors (e.g., weather, political instability). These all factors will affect the delivery of equipment and other items on construction site.
3. Labor and Staffing Issues:
   • Difficulty in hiring skilled labor. To complete a projects we need skilled labour and this comes with a cost. If we try to control the project cost and compromise with the quality of labour this will certainly impact work quality and delay in project work completion.
   • High turnover rates or lack of employee retention. During plant construction we keep on hiring the engineers, technicians, fitters and other staff. But at that time work load is of different in nature, like supervision of plant construction, study and understanding of new processes, training, etc. So keeping employing engaged is a tough challenge, therefore many employees leave in between for some better opportunities in running plant.
   • Safety concerns and ensuring a safe working environment. In a plant under construction maintaining safety is very difficult work, as fabrication, rigging, insulation, instrumentation, electrical work is in process. Hence, there are lots of chances of accidents and to control those is a big task for a safety officer.
4. Financial and Budgeting Problems:
   • Underestimating operational costs. When plant is mechanically completed and commissioning starts our main focus remain to run the plant only. We are least bothered about the production capacity, raw material & utility norms. This loss is the part of plant start up cost or pre-operative cost. If plant commissioning takes more time then envisaged then project completion cost will increase and we need to arrange the funds to meet the requirements.
   • Securing necessary funding or managing cash flow. For the project manager and finance controller it is a very big challenge when project is delayed and performance is not meeting with design parameters. In such situation we need additional funds to pump into the plant till all the issues are resolved and plant is running on its designed parameters (i.e., capacity, RM & Utility norms, effluent norm, product quality).
   • Variations in market demand or product pricing. For a business head it becomes a very disturbing situation, when the plant is successfully commissioned and demand is low or product prise drops. This will impact financial feasibility of the investment and increase the capex pay back period. Some times whole capex expenditure comes under huge loss to the organization if that product is ban or out of use.
5. Regulatory and Compliance Hurdles:
   • Navigating local, state, or federal regulations. For a marketing manager to sell the product across states comes under various rules and regulation. When any rule is unfavourable is affects the product sale negatively and leads to the revenue loss.
   • Meeting environmental standards and obtaining necessary permits. If in original plant design we do not ponder over various effluent generation, their capacity and quality, it can be a big nightmare for a plant manager and site head. Because we can not discharge any effluent be it gas, liquid or solid in to the environment without treatment. Therefore, we need to install the ETP, CETP, Incinerators, Thermal Oxidizers, spray dryers, vent gas scrubbers for the treatment of various effluent streams to meet the environmental standards.
   • Adhering to industry-specific regulations. If we are running a industry then it is mandatory to abide with the rule and regulation of the land.
6. Operational Efficiency:
   • Optimizing production processes for maximum efficiency. After plant commissioning to meet the market challenges and remain in competition we need to keep continue to work upon product cost reduction and productivity enhancement. For this purpose we need to train the employees for TPM (Total Productive Maintenance), Lean & Six Sigma.
   • Managing waste and minimizing resource consumption. Our process excellency or operational excellency team can work upon the processes to reduce, reuse and recycle schemes of the various waste. In absence of this initiative the product cost will increase and it will reduce the company profit margins.
   • Ensuring smooth coordination across departments. Because an organization is the group of various functions like operation, supply chain, Human Resource & training, Design & Projects, Business, Finance, Operational Excellence, Safety & Environment, Quality, R&D, etc. If there is poor coordination among these groups, respective group people have personal ego greater than organization benefit then it is a disaster. Any successful organization keeps growing if there is efficient communication and smooth coordination across the departments.
7. Quality Control and Customer Expectations:
   • Ensuring that products meet quality standards consistently. Any mistake of quality control department during sample testing can create a big problem for business. The customer will reject the material and it return back to the factory. Reprocessing of the off spec or low quality product is a additional cost and simultaneously is a dent to the brand value.
   • Managing customer expectations and complaints. If quality control department is not addressing the customers complaint timely, then it is possible that we can loose the business. Also it will spread bas name for the organization.
   • Implementing feedback loops for continuous improvement. When a complaint is received, it should be logged promptly, and the urgency and impact assessed. From there, a thorough root cause analysis is carried out—often using methods like the 5 Whys or a Fishbone Diagram—to dig beyond surface symptoms and uncover the real issue. Once identified, corrective actions are taken to address the root cause directly.
   • But it doesn’t stop there. Preventive actions are just as critical. These are designed to stop the issue from recurring—not just in the affected product, but across similar systems or operations. Clear, timely communication with the customer is maintained throughout the process, sharing updates and outcomes transparently.
   • Every step is documented and reviewed, and the CAPA is only closed once effectiveness has been verified. Over time, analyzing these cases can reveal patterns that help drive continuous improvement and build stronger, more resilient processes.
   • In short, CAPA isn’t just about fixing what went wrong—it’s about learning from it, so it doesn’t happen again.
8. Environmental Factors:
   • Weather conditions and natural disasters can significantly delay plant start-up by disrupting construction schedules, damaging infrastructure, or hindering the delivery of equipment and materials. Heavy rains, floods, storms, or extreme temperatures can halt on-site activities and pose safety risks to workers. In severe cases, natural disasters like earthquakes or cyclones can cause structural damage, requiring repairs and reassessments before commissioning can proceed. Such delays can impact project timelines, increase costs, and require contingency planning in high-risk areas.
   • Sustainability concerns and environmental impact can pose significant challenges during plant start-up, particularly in industries with high emissions, effluent discharge, or hazardous waste generation. Regulatory compliance has become more stringent, requiring detailed environmental impact assessments, pollution control systems, and waste treatment solutions to be operational from day one. Delays in obtaining environmental clearances or issues with effluent treatment plant (ETP) performance can stall commissioning activities. Additionally, communities near industrial zones are increasingly vocal about ecological risks, prompting greater scrutiny from authorities and stakeholders. Sustainable sourcing of raw materials, energy efficiency, and carbon footprint reduction must also be integrated into process design, often necessitating modifications late in the project cycle. These factors not only affect timelines and budgets but also demand a more proactive approach to environmental management, making it a critical consideration in successful and responsible plant start-up.
9. Navigating local community relations, especially if the plant has environmental concerns
   • Especially when there are environmental concerns involved. Resistance from nearby residents—due to fears of pollution, water usage, or health impacts—can lead to protests, legal actions, or demands for additional safeguards. Gaining community trust often requires extensive engagement, transparency, and sometimes redesigning parts of the project to address public concerns. Without early and consistent communication, local opposition can escalate, prompting regulatory reviews or halts in construction, ultimately delaying commissioning and operations.

Conclusion

Problems rarely end with project initiation—they persist through commissioning and often continue even after start-up. That’s why it’s crucial to anticipate potential challenges early and develop proactive strategies and contingency plans to manage them effectively. By foreseeing issues related to design, regulations, environment, community relations, and operations, we can minimize disruptions and maintain smooth, efficient business operations. Preparedness not only reduces delays and costs but also builds resilience and ensures long-term success.

Thanks for Reading.

The post Challenges after a Plant Commissioning appeared first on ChemEnggHelp.

With over 25 years of experience in chemical plant design, process optimization, and digitalization, I have witnessed firsthand how expert consulting can bridge the gap between technology and profitability. Let’s explore the key responsibilities and value additions that a consultant brings to chemical process industries.

1. Feasibility Studies & Conceptual Design

A successful project begins with a robust feasibility study. This involves:

• Process Selection: Evaluating raw materials, reaction pathways, and technology options. So that capex investment is safe and provide highest possible returns to the investors.
• Techno-Economic Analysis: Assessing CAPEX, OPEX, and ROI to determine economic viability. Selecting best possible technology in terms of initial capital requirement. Choosing contemporary technology which is providing highest product yield, lowest cost of manufacturing and generating low waste which is not toxic and hazardous.
• Process Flow Development: Creating initial Process Flow Diagrams (PFDs) and performing mass & energy balances. This will help to understand the process at macro level to the stockholders and enables to estimate cost of production data for financial feasibility study.
• Risk Analysis: Identifying potential challenges related to safety, sustainability, and regulatory compliance. Assessment of the safety equipment requirement, process controls, material handling, selection of effluent treatment, required provision during plant design & engineering.

2. Process Design & Engineering

Once feasibility is established, the consultant plays a pivotal role in detailed process design:

• PFDs & P&IDs: Developing block flow and process flow diagram, carryout the material and energy balance for the process. Subsequently designing of process control system with process and instrumentation diagrams.
• Equipment Sizing & Selection: Designing and preparation of specification sheets of unit operation such as reactors, distillation columns, heat exchangers, pumps, and separators.
• Process Simulations: Using advanced tools like ChemCad, HYSYS, and other simulators to optimize process conditions. The detailed design of heat exchangers, distillation & absorber columns.
• Safety Considerations: Conducting HAZOP studies, SIL assessments, and relief system design to mitigate risks.

3. Detailed Engineering & Project Support

A chemical process consultant collaborates with multidisciplinary teams to ensure smooth project execution:

• Material & Equipment Specification: Providing detailed guidelines and equipment specification data sheets for procurement and fabrication. This includes all the required details including equipment operating parameters (i.e., flow rate, capacity, pressure, temperature), design parameters and material of construction, applicable codes & standards for equipment design and testing, sketch of the equipment with nozzle schedule, site conditions, etc.
• Process Control & Automation: Defining instrumentation requirements, control schemes, and digital monitoring solutions. After detailed study of the chemical process, we design a control philosophy for the smooth and efficient plant operation. In this course of work we take into consideration emergency plant shutdown requirements to avoid any hazardous conditions.
• Vendor & Licensor Evaluations: Analysing technology proposals for proprietary processes, identify optimal solutions, assess technological options to minimize variable production costs, and study effluent generation, treatment methods, and environmental impact.

4. Process Optimization & Troubleshooting

Even well-designed plants require continuous optimization and this is imperative for businesses to remain competitive. To meet this objective, a consultant applies tools like Six Sigma & Lean and can provide solutions for:

• Energy & Yield Optimization: Applying DMAIC & Lean methodology, Implementing heat integration, advanced process controls, and AI-driven analytics.
• Debottlenecking & Capacity Expansion: By process mapping and using Lean methodology to Identify the constraints or debottleneck stages. This way improving throughput without major capital investment.
• Operational Issues: Analysing process data using six sigma tools and troubleshooting quality, yield, or equipment performance problems.

5. Sustainability & Green Chemistry

With increasing regulatory pressure and environmental concerns, sustainability is at the core of modern plant design. To meet this objective we need to work upon below line items:

• Waste Reduction & Byproduct Recovery: Enhancing material efficiency to minimize waste. Finding the possibilities of recycling & reusing the effluent streams inside the plant. Working upon options to convert the waste into wealth so that final product can more economical and sustainable.
• Carbon Capture & Green Energy Integration: Exploring alternative energy sources and emission control strategies. We can study the process and work upon the methods to recover waste heat available from heat of reaction, distillation column condensers, high temperature streams and flue gases. This way we can reduce the overall energy requirement for the plant and can reduce the carbon foot prints.
• Eco-Friendly Processes: To design a sustainable and green process, evaluation of renewable feedstocks, green solvents, and low-carbon production methods.

6. Commissioning & Startup Support

Consultants play a hands-on role in plant commissioning and startup. Since he or she has complete knowledge of process technology and plant, therefore can anticipate the possible hurdles and problems during commissioning. Also, previous experience gives hands of solutions to resolve the issues which helps to expedite the plant start up:

• Pre-Startup Safety Reviews (PSSR): Ensuring that the plant meets all design and safety criteria. This step help to avoid any unforeseen issues which can lead to accident or equipment breakdown before commissioning. This includes to check the issues like missing of gaskets, bolts, welding joint failure, electric motor direction, any blind availability, NRV fitting, strainer or filter chocking, safety valves, vents & drain provisions, etc.
• Operator Training: Conducting workshops on plant operation, troubleshooting, and digital tools. This is an important step before plant handover to the production team. Also, preparation and review of the plant standard operating procedures before actual plant commissioning is very crucial.
• Performance Validation: Analysing startup data to confirm that the plant is operating as per design expectations. In case there is any gap in plant performance then conducting brainstorming to fix the problems so that design parameters can be achieved.

7. Compliance & Regulatory Support

Navigating the complex landscape of industry regulations is another critical aspect:

• Environmental & Safety Regulations: Ensuring compliance with OSHA, EPA, REACH, and other global standards.
• Documentation & Permitting: Preparing necessary reports and technical documentation for regulatory approvals.
• Risk Management: Conducting safety audits and implementing best practices for chemical handling.

How a Consultant Adds Value

• Independent & Unbiased Perspective: Unlike in-house teams, consultants provide objective insights.
• Cost Savings: Optimizing CAPEX & OPEX through smarter engineering and technology choices.
• Innovation & Digitalization: Leveraging real-time analytics, AI, and machine learning for better plant control.
• Risk Mitigation: Proactively identifying and resolving potential failures.

Conclusion

In an industry where margins are tight and efficiency is key, the right consulting expertise can mean the difference between success and failure. Whether you are planning a new project, troubleshooting an existing plant, or looking for digital transformation solutions, expert consulting can help unlock new levels of productivity and sustainability.

If you are looking for a consultant with deep experience in chemical plant design, process improvement, and digital transformation, feel free to reach out. Let’s work together to build the future of chemical manufacturing!

Thanks for reading,

Kailash Mehra

The post The Role of a Chemical Process and Plant Design Consultant appeared first on ChemEnggHelp.

A poorly designed feed pipe distributor can cause back flow. This we can see in case of low pressure drop across the distributor holes. While, in case of high pressure across the distributor holes causes jet & mist formation, which may lead to emulsion formation in case of liquid liquid extraction column.

Liquid Pipe Distributor Sizing

Below is the sample calculation to size the pipe distributors for a liquid-liquid extraction column:

Conclusion

Above calculation is helpful to size a pipe distributor for a given liquid feed. A properly designed distributor is very critical for the best performance of the absorber column, extraction column or distillation column.

Thanks.

The post Pipe Distributor for Liquid appeared first on ChemEnggHelp.

Different Types of Structured Packings

For example, Mellapak 250Y is a less denser structured packing and mostly used where we are looking for highest vapour or gas throughput rates and low theoretical plates per meter of packed height. While, Mellapak 750Y or gauge packing like BX & CY are used where we are looking for highest number of theoretical stages in per meter of packed height. Here, we can get around 8-10 stages. But these packing packings are good for low liquid flow rates and gas throughput rates.

Once we get the superficial velocity through column for a given structured packing, using the velocity and volumetric flow rate we can calculate column diameter.

Flow Area (m2) = Volumetric Flow Rate (m3/s)/ Superficial Velocity (m/s)

Diameter (mm) = 1128.4*(Flow Area^0.5)

Superficial Velocities for Different Structured Packings

In below table there are the values of superficial velocities which we can use to estimate the packed column diameter for given vapour load. In my experience I found these values are very close to actual plant operation. These values are good for atmospheric column operation. For vacuum operation we can use higher superficial velocities than this, around 3-4 times of the given values.

Conclusion

Column diameter depends on vapor or gas volumetric flow rate through the column. And, volumetric flow rate is the function of column pressure. At higher pressure, vapour density will be higher and volumetric flow rates will be lesser. On other hand, in vacuum while density is low therefore we can afford higher superficial velocities through the column. In summary, we can say if we operate a column in vacuum, which was designed for atmospheric conditions, the capacity of that column will reduce. As, at higher gas velocities column will lead to flooding conditions.

Thanks,

The post Packed Column Diameter Estimation appeared first on ChemEnggHelp.

Process Description

Let us assume a homogeneous liquid phase non-catalytic reaction. In this reaction two organic raw materials, chemical ‘A’ and chemical ‘B’ reacts to form chemical ‘C’. This is an exothermic reaction and raw material ‘A’ is limiting reactant. Chemical ‘B’ consumption is 1.25 times of reactant ‘A’. Heat of reaction is 150 kcal/kg of reacted ‘A’.

 In this process equilibrium conversion of the reaction is 85% on the mass basis for reactant ‘A’. This reaction takes place at 85 ⁰C and atmospheric conditions. Selectivity of the reaction is 95% on mass basis. And remaining 5% of reacted ‘A’ converts into high boiling tar like material. This residue composition is as below which is sent for incineration. The calorific value for residue is 7500 kcal/kg approximately.

Physical and Chemical Properties

For our batch reactor process calculations, we need physical and chemical properties for the chemicals are in below table.

A (liq.) + B (liq.) —->  C (liq.)      at 85 ⁰C and atmospheric pressure, below is the process flow diagram for our batch reactor system.

Process Flow Diagram (PFD)

Here,

RM – Raw Material

CWS – Cooling Water Supply

CWR – Cooling Water Return

Cond. – Steam Condensate

Material Balance for the Batch Reactor System

This process includes two steps first is reaction and second is batch distillation. The material balance for per batch will be as below.

• Charge of RM – A, 2000 kgs/batch
• Charge of RM – B, 2500 kgs/batch (since B is charged 1.25 times of A)
• Total mass of in reactor (RM – A + RM – B = 4500 kgs/batch)
• Equilibrium conversion is 85% hence unreacted RM – A in crude product = 2000*(100 – 85)/100 = 300 kg.
• Unreacted RM – B in crude will be = 300*1.25 =375 kg.
• Product C in crude will be (2000 + 2500) *0.85*0.95 = 3633 kg (since selectivity is 95% for the product C.)
• Heavies’ generation in reaction will be = (2000 + 2500) *0.85*0.05 = 181.7 kg/batch. Since the composition of heavies in residue is 95% hence residue generation per batch will be = 181.7 *100/95 = 191.3 kg.
  • Loss of RM – A in residue will be 191.3 *1/100 = 1.91 kg/batch
  • Loss of RM – B in residue will be 191.3 *2/100 = 3.83 kg/batch
  • Loss of Product C in residue will be 191.3 *2/100 = 3.82 kg/batch

• The recovered quantities from distillation based on 90% recovery will be as below (given in R&D technology package).
  • RM – A recovered = 300 *90/100 = 270 kg/batch
  • RM – B recovered = 375 *90/100 = 337.5 kg/batch
  • Product – C recovered = 3633 *90/100 = 3269.7 kg/batch
  • Intercut quantity of A & B = 45.5 kg/batch (66% A and 34% B) – from R&D package
  • Intercut quantity of B & C = 44.0 kg/batch (50% B and 50% C) – from R&D package
• Total production of product – C will be = product in crude – loss in intercut – loss in residue = 3633 – 22 – 3.82 = 3607.2 kg/batch.
• Total RM – A consumed = Charged – Recovered = 2000 – 270 = 1730 kg/batch
• Total RM – B consumed = 2500 – 337.5 = 2162.5 kg/batch

Energy Balance for the Batch Reactor System

Heating utility for our process is 3.5 bar steam at saturated conditions. The temperature of the steam is 139 ⁰C and latent heat is 513.5 kcal/kg. 

Steam Requirement

• Heat load for reaction mass heating after charging of RM – B will be Q1 = mass RM-B * Cp * (initial temp – final temp) = 2500*0.35*(80-35) = 39375 kcal/batch. Hence steam requirement will be m1 = Q1/513.5 = 76.7 kg/batch.
• Heat load and steam requirement in distillation will as follows:
  • For recovery of RM – A, heat load will be Q2 = mass recovered * (1 + reflux ratio) * latent heat = 270*(1 + 5) *100 = 162000 kcal/batch. Steam requirement will be m2 = Q2/513.5 = 162000/513.5 = 315.5 kg/batch.
  • Similarly, for RM – B recovery Q3 = 337.5*(1 + 10)*100 = 371250 kcal/batch. Steam requirement will be m3 = Q3/513.5 = 723.0 kg/batch.
  • For product recovery Q4 = 3269.7*(1 + 10)*90 = 3237003 kcal/batch. Steam requirement will be m4 = Q4/513.5 = 3237003/513.5 = 6303.8 kg/batch.
  • For first intercut Q5 = 44.5*(1 + 25)*100 = 115700 kcal/batch. Steam required will be m5 = Q5/513.5 = 225.3 kg/batch.
  • Heat load for second intercut Q6 = 44.0*(1 + 40)*100 = 180400 kcal/batch. Hence steam requirement will be m6 = Q6/513.5 = 351.3 kg/batch.

Therefore, total steam requirement for total batch processing will be Q = Q1 + Q2 + Q3 + Q4 + Q5 + Q6 = 76.7+315.5+723.0+6303.8+225.3+351.3 = 7995.6 kg/batch. Considering 5% steam loss actual steam requirement will be Q’ = 1.05*Q = 8395 kg/batch.

Cooling Water Requirement

Cooling water flow rate requirement will be based on when our reaction is going on and pure product draw is going on. As this will be maximum requirement any point of time during the process.

• Hence, heat load on jacket during reaction q1 = rate of addition A * heat of reaction = 500 * 150 = 7500 kcal/h (for calculation we are considering 100% conversion). Cooling water supply and return temperature are 32 and 40 ⁰C respectively. Hence, cooling water flow will be w1 = q1/(Cpw*(40-32)) = 7500/(1*(40-32)) = 937.5 kg/h.
• Heat load during pure product draw (3269.7/10 = 327 kg/h) will be q2 = 327*(1 + 10) *90 = 323730 kcal/h. Therefore, cooling water requirement at column condenser will be w2 = q2/(Cpw*(40-32)) = 323730/(1*(40-32)) = 40466 kg/h.
• Water circulation in reactor condenser w3 = 5000 kg/h.

Total flow rate for cooling water pump will be W = w1 + w2 + w3= 937.5 + 40466 + 5000 = 46403.5 kg/h or 46.4 m3/h.

Power Requirement

Cooling water pump will be 50 m3/h and 30 m head. Hence power consumption will be P1 = m*9.81*h/(3600*pump efficiency) = 50000*9.81*30/(3600*0.75) = 5450 W = 5.45 kW. Total consumption per batch will be P1’ = P1*Batch Cycle Time = 5.45*27 = 147.15 kW/batch.

Reactor and distillation vessel agitator motor power is 5.5 kW. Hence power consumed by agitator motors will be P2 = Reactor agitator* operating hours + Distillation agitator* operating hours = 5.5*570/60 + 5.5*1050/60 = 148.5 kW/batch.

Other transfer pumps and auxiliary power requirement P3 = 60 kW.

Total power requirement will be P = P1’ + P2 + P3 = 147.15 + 148.5 + 60 = 355.65 kW.

Norms Estimation

RM – A consumption norm = Consumption A/Production of C = 1730/3607.2 = 0.4796 kg/kg

RM – B consumption norm = Consumption B/Production of C = 2162.5/3607.2 = 0.5995 kg/kg

Residue generation norm = Residue generation/Production of C = 191.3/3607.2 = 0.053 kg/kg

Steam consumption norms = Q’/3607.2 = 8395/3607.2 = 2.327 kg/kg

Power requirement will be = P/3607.2 = 355.65/3607.2 = 0.099 kW/kg

Cycle Time Estimation for Batch Reactor System

Listing down unit operation wise all the steps in batch reactor process system and adding the time taken in each process step provides the cycle time for that process step. Below is the table and sample working for your understanding:

In our example there are two process steps, first is reaction and second is distillation. From above table we can see in batch reactor total time cycle is 570 min and in distillation step batch cycle time is 1050 min. Therefore, effective batch cycle time for this process will be whichever is highest and here it is distillation step. So, batch cycle time or BTC of this batch process is 1050 min. While overall batch time cycle is (570+1050= 1620 min).

Conclusion

You can use this procedure to carry out the material and energy balance for the batch reactor plant. For your work you will get a technology package from your R&D department. In this you will get all the information regarding reaction and downstream requirement. After this we do the equipment design for equipment. In our example various equipment are such as reactor, reactor condenser, transfer pump, distillation vessel, distillation column, column condenser, etc.

Next, we design control system requirement for reactor temperature, distillation column temperature, steam flow and reflux flow. Pipe line sizing for process, cooling water, steam and condensate.

P&ID development, equipment layout and elevation drawings are developed subsequently. In my future post we will go through all the steps.

Thanks,

The post Material & Energy Balance for Batch Reactor appeared first on ChemEnggHelp.

Steam Economy

The steam economy for a MEE is (kg of steam used/kg of water evaporated from all effects). We can enhance steam economy by increasing number of effects. However, we should evaluate the steam economy v/s fixed cost for the MEE. In our industries most of the effects are 3 or 4 stage only. Using higher number of effects will not increase steam economy substantially, while investment required will be more. Some of the applications where we use MEE are as below:

• Concentration of aqueous feed of Vitamin before feeding into the dryer.
• Raw spent wash concentration before feeding into slop fired boiler.
• Concentration of lean organic effluent stream before feeding into the incinerator and reducing fresh water requirement by recycling evaporated water.
• Waste water concentration, which contain various salts (i.e., NaCl, Na₂SO₄, (NH₄)₂SO₄, etc.) and recycle the evaporated water to reduce the fresh water and final effluent quantities.

Types of MEE Systems

Based on the feeding orientations, we can categorize MEE operation as described below:

Forward Feed Operation

In this operation the feed enters into the first effect via feed pump and then subsequently flow through all the effects in downstream. Similarly, vapour from first effect enters into second and continue till the last effect. In this operation lowest temperature is at the last effect as pressure in effects keep on decreasing. Therefore, this kind of arrangements are good where final concentrated product is heat sensitive. Below is the figure for your reference:

Backward Feed Operation

Here, feed enters into the last effect and the concentrated product we collect from the first effect. To understand this operation, you can refer to below figure. Here, feed flows from low temperature & pressure to higher temperature & pressure. Which is in contrast with feed forward operation. This type of arrangement is advantageous when final product is viscous. As, with decrease in temperature viscosity increases, therefore it is better option to use feed backward MEE system. This way concentrated product after each effect is at higher temperature and at higher temperature viscosity will be lower. 

Other Feed Operations

Apart from above we can use mix feed operation mode also, which is the combination of feed forward and feed backward operations. In mixed feed the dilute liquid enters in between of effects, flows in forward feed to the end of the effect and then pumped back to the first effect for final concentration. Also, MEE can be natural circulation or forced circulation type.

You can see another common evaporator arrangements as shown in below figure, which is more common in crystallizations. This we know as parallel feed operation. In this feed enters individually to all the effects. While, vapour from first effect enters into the second effect and continue to travel till last effect.

To improve steam economy, vapour compression may be applied to the vapour from the first effect of a multiple effect system. Thus, giving increased utilization of the steam for the MEE system. However, such a device is not suitable for use with liquid feeds with a high boiling-point rise. Because in this case, we need to compress the vapors at high pressure to superheat, so that it can provide heat to next calendarial. Finally, this will reduce the energy efficiency.

Simulation Results of a Three Effect MEE

Below is the material & energy balance of a four-effect feed forward evaporator system. In this multiple effect evaporator we are concentrating a NaCl water solution containing from 3.00 to 23.90% by wt. Feed rate in first effect is 15000 kg/h at 40 ⁰C.

First effect is operating at 1.6 bar pressure and last effect which is fourth one is operating at 0.1 bar pressure. These are absolute pressure not gauge, so in gauge pressure 1^st effect is at 0.6 bar positive pressure and 4^th effect is 0.9 bar vacuum. Corresponding temperatures for 1^st & 4^th effects are 113.33 ⁰C and 45.75 ⁰C respectively. Apart from this 2^nd effect is operating at 85.93 ⁰C and 3^rd effect is at 75.84 ⁰C.

In first effect evaporator we are using 9.0 bar saturated steam having temperature 175.43 ⁰C, which has condensate outlet temperature at 155 ⁰C.

The overall boiling point difference is: 113.33 – 45.75 = 67.58 ⁰C

Total water evaporation quantity is: 13117 kg/h (1^st effect: 2791 kg/h, 2^nd effect: 3305 kg/h, 3^rd effect: 3426 kg/h & 4^th effect: 3594 kg/h)

Steam feed rate to first effect is: 2900 kg/h

Hence steam economy for this MEE is: 2900/13117 = 0.221 kg/kg

Cooling water requirement (32 ⁰C supply and 36 ⁰C return) is: 518.6 m³/h

Conclusion

The intent of this article is to understand types of multiple effect evaporators and their operation. Also, we discussed one example of four effect evaporator. We gone through the material and energy balance. I guess, this will help you to carryout the material and energy balance for your multiple effect evaporator requirement.

You can sustain the performance of the MEE by arresting the leakages and removing the scale formed in evaporator by high pressure and chemical cleaning processes. Because both the problems will decrease the overall temperature gradient between first and last effect. Other than this cooling water supply temperature at last effect vapour condenser is very important. If cooling water supply temperature is higher it will increase the condensing vapour temperature and will reduce vacuum also. In result this will reduce the efficiency of MEE. Moreover, you should regularly clean the condenser from cooling water side.

Thanks for your reading.

The post Multiple Effect Evaporator appeared first on ChemEnggHelp.

In this article I will discuss about the pressure safety valve and its specification sheet. The pressure relief valve (PRV) could also be referred to as a pressure safety valve (PSV) and relief valve. Any system operating at pressure such as vessels, reactors or tanks requires safety devices. These safety devices are mainly safety valves or rupture disc which can protect plant, people & process. We can define a safety valve as a safety device, which automatically open, without the assistance of any energy other than that of the fluid concerned. And, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded. Moreover, which is designed to re-close automatically and prevent further flow of fluid after normal pressure conditions of service have been restored.

Design of Safety Valve

Below is the figure, which you can refer to understand the design of a typical safety valve:

In below specification sheet you can provide various data & information for the supply of a suitable safety valve. Below is the format for PSV specification for your reference.

In above specification sheet you can provide various data for the required pressure safety valve (PSV). It has various sections in which you can provide details like General, Connection (here we provide size & rating for inlet/outlet connections). In Material section we provide the materials of construction for the various parts of the safety valve. We can provide the details for design Code and design basis (i.e., for blocked flow or fire case) in Basis section. Fluid properties we can provide in Fluid Data section. While Other Data section contains that information which pressure safety valve supplier will be provide based on selected and designed PSV.

Safety Valve Sizing

A process engineer needs to provide the sizing data to the safety valve supplier, so that based on that vendor can design or select an appropriate pressure safety valve. To understand this safety valve sizing exercise, we will take an example of pressurized vessel containing ammonia. Below are the details for the storage vessel:

To estimate the capacity for safety valve we can look in two ways, first is blocked flow case and second is fire case. Blocked flow means when in-flow is ON inside a pressure vessel and out-flow is blocked. In that case the pressure inside the vessel will keep on increasing. So, to release the excess pressure in blocked flow condition required release capacity will be equal to the in-flow rate of the stream.

Second, for fire case when there is fire surrounding the vessel. Then, there will be heat ingress into the vessel through the surface and liquid inside the vessel start boiling and pressure start increasing inside the vessel. In this case to restore the vessel pressure, relief valve releases the excess vapour generating because of rate of heat ingress during fire.

So, after looking for both the cases which ever flow is higher between blocked flow and fire case, we consider that as capacity for the pressure relief valve.

Flow Capacity Estimation in case of External Fire

Below formula you can use to estimate heat inflow rate during external fire. After estimating heat input rate dividing it by latent heat of vaporization of the fluid you can estimate mass flow rate of vapour generation.

Safety valve release capacity for fire case = Q / Latent Heat of Vaporization

So, first you get the mass flow rate for both the condition (i.e., input mass flow rate and second mass flow rate for external fire). Between these two mass flow rates, whichever mass flow rate is higher, we consider it as design mass flow rate for the relief valve. This data we know as require capacity (kg/h) for the pressure relief valve.

Types of Pressure Safety Valve

We can find mainly below types of PSV or PRV in our plants:

Balanced Pressure Safety Valves

When back pressure is > 10% of the set pressure at 10% allowable overpressure, we should use balanced pressure relief valves. Because a conventional PRV shows unsatisfactory performance when excessive back pressure develops during relief of excess fluid. This excess pressure builds up due to the fluid flow though the valve and outlet piping. Therefore, to handle this issue, we use a balanced pressure relief valve to decrease the backpressure effects. Simultaneously it protects the bonnet spring and guide from released fluids in case of corrosive fluid services.

Conventional Spring Loaded

We can use a conventional spring loaded PRV, where built up back pressure is <10% of the set pressure at 10% allowable overpressure. In addition to this, these PRVs are suitable for non-corrosive services as well. Conventional spring-loaded valves consist of the bonnet, guide, and spring in the released fluids. As the bonnet vents into the atmosphere, the relief-system back pressure lowers the set pressure. However, as the bonnet vents inward to the outlet, the process is reversed and the relief-system backpressure makes the set pressure higher.

Pilot Operated Safety Valve

This type of PSV is a self-contained system. And, these type of safety devices does not require any external power or pressure source to operate it. Here, the operation of safety device is initiated and controlled by the fluid discharged from a connected pilot valve. This pilot valve is a direct spring-loaded safety valve designed for the required pressure conditions.

Conclusion

So, I guess you can prepare specifications for a safety valve using this article. Also, to download the specification sheet format for your help please click here. Also, please note a safety valve is useful when pressure increase in a system is gradual. Which is the scenario in case of in blocked flow or external fire case. While, wherever there are chances of explosion or reaction run away. We need to provide a rupture disc to release the sudden pressure rise. Because a rupture disc can burst at a set pressure immediately to release the pressure immediately to protect the equipment.

Finally, always we should first look for a safer design. And, subsequently provide adequate safety devices to protect the people, process & plant.

Thanks for reading..

The post Safety Valve appeared first on ChemEnggHelp.

Details of Column Costing Sheet

So, first let us discuss the distillation column costing sections. Generally, we can divide this in following sections:

Material Cost

This includes the cost of material purchased which is required for the fabrication of the distillation column. For costing purpose, we need to consider raw material cost which includes finished equipment weight and waste material. Waste material is the remaining metal after cutting out the required portion of metal from sheets and pipes. This is around 10% of the finished equipment weight. The various types of material include plates for shell, channel & dish ends, plates for flanges, plates for skirt support, material for ladder & platforms, nozzle pipes & flanges, material for column attachments, etc.

Fabrication Cost

For distillation column fabrication there are lots of activities involved which are performed by skilled fitters & welders. Based of the fabrication drawing cutting, plates rolling & welding is done. The fabrication of body flanges in case of segmented columns. While in case of single piece monobloc column we need to fabricated ladders & service platforms for access of manholes. So, charges of fitters & welders, consumables for welding & cutting, various machine charges, electricity charges, etc. are the part of equipment fabrication cost. This fabrication cost is generally in the range of 30% to 50% of the total material cost. For small size and complicated equipment fabrication cost is considered higher side (i.e., 40-50% of material cost). While for simple and large size equipment we should take fabrication cost lower side (i.e., 30 to 40% of the material cost).

Cost of Column Internals

Other than above we need the costing for column internals also. In our plant either we use packed column or tray type columns. So, for the costing of packing whether it is structured or random can be taken from vendors or you can refer to past purchase orders. Once you have per m3 cost of the packing, this can help you to estimate the column packing cost. And, for the costing of plates we can estimate the weight of single plate and multiply it with material and fabrication cost. However, it is better if we get this cost from tray supplier directly or can refer some past purchase orders.

Other Cost

This comprises various charges like testing and inspection, painting and insulation (if done at vendor site), taxes & freight charges are also the part of this cost. Other than this packing & forwarding is also the charges which add to the final equipment cost.

Distillation Column Costing Spread Sheet

Below is a format to do the costing for distillation column, in which you need to provide various data of a distillation column or other columns (i.e., extraction, absorber, stripper, etc.). To furnish these data, you need distillation column data sheet or fabrication drawing.

Input Values

Please provide all the inputs as marked as red, such as diameter, shell length, shell plate thickness, channel shell length, thickness of channel shell & dish ends, flange thickness, etc. Apart from this you can provide the nozzle details in nozzle table for their weight estimation. You can customize this based on your requirement if there is change in flange rating.

Moreover, in case you wish to have lined body flanges you can change this accordingly. For that we need to change the MOC of body flanges from SS to MS or CS and change the total weight for SS & MS will change accordingly. Similarly, if there is change in the type of column you need to input data in this sheet accordingly. However, this sheet can be used for segmented column or single piece column (i.e., monobloc type) costing estimation. In above figure, I have considered a segmented distillation column (having body flanges) having six segments. Made of SS304 body and CS flanges having SS304 liners to reduce the equipment costing.

Apart from these you need to provide material cost and fabrication cost, which is latest one. This you can easily get from the purchase department people. To download the excel sheet for shell & tube heat exchanger please click here.

Conclusion

I am sure this will help you for distillation column cost estimation. Furthermore, you can modify this calculation sheet as per your requirement to estimate the costing for absorber column, stripper column, extraction column, etc. Apart from this cost of column internals such as trays, packing (i.e., random or structured) we can get from vendors or refer to the past orders.

Thanks for reading.

The post Distillation Column Cost Estimation appeared first on ChemEnggHelp.

Sections of Equipment Costing Sheet

So, first let us discuss the various sections of the shell and tube heat exchanger costing. Generally, we can divide this in following sections:

Material Cost

This part includes the cost of material which you procure for the fabrication of the heat exchanger. For costing purpose, we need to consider raw material cost which includes finished equipment weight and waste material both. Waste material is the remaining metal after cutting out the required portion of metal from sheets and pipes. This is around 10% of the finished equipment weight. The various types of material include plates for shell, channel & dish ends, plates for flanges, plates for tube sheets, plates for baffles, tubes, tie roads, nozzle pipes & flanges, material for support, etc.

Fabrication Cost

For the heat exchanger fabrication there are lots of activities involved which are performed by skilled fitters & welders. Based of the fabrication drawing workers do cutting and welding of the plates, tubes, pipes & flanges. Drilling of the tube-sheets, baffle plates and fabrication of the body flanges is done. So, charges of fitters & welders, consumables for welding & cutting (i.e., welding rods, cutting wheels, gas cylinders, etc.), various machine charges, electricity charges, etc., are the part of equipment fabrication cost. This fabrication cost is generally in the range of 30% to 60% of the total material cost. For small size and complicated equipment fabrication cost is considered higher side (i.e., 40-60% of the material cost). While for simple and large size equipment we should take fabrication cost lower side (i.e., 30 to 40% of the material cost).

Other Costs

This comprises various charges like testing and inspection expanses, painting and insulation (if done at vendor site), taxes & freight charges are also the part of this cost. Other than this packing & forwarding is also the charges which add to the final equipment cost.

Format of Shell and Tube Exchanger Costing

Below is a typical format to do the costing for a shell & tube HE, in which you need to provide various data of the shell & tube heat exchanger. To furnish these data, you need heat exchanger data sheet or fabrication drawing.

Input Values

Please provide all the inputs as marked yellow, such as diameter, shell length, shell plate thickness, channel shell length, thickness of channel shell & dish ends, number of tubes, tube sheet thickness, flange thickness, numbers of baffles & thickness. Apart from this you can provide the nozzle details in nozzle table for their weight estimation. You can customize this based on your requirement if there is change in flange rating.

Moreover, in case we wish to have lined body flanges we can change this accordingly. For that we need to change the MOC of body flanges from SS to MS and change the total weight for SS & MS accordingly in the excel sheet. Similarly, if there is a change in the type of exchanger you need to modify this excel sheet accordingly. However, this sheet you can use for BEM or AEN type shell & tube heat exchangers costing. Also, here I have considered a BEM type heat exchanger with CS body flanges having SS304 liners to reduce the equipment costing.

Apart from these you need to provide material cost and fabrication cost, which should be latest one. This you can easily get from the purchase department people. To download the excel sheet for costing of shell & tube heat exchanger please click here.

Conclusion

I am sure this will help you to estimating the cost of a shell & tube heat exchanger. Furthermore, you can modify this calculation sheet as per your requirement to estimate the costing for reboiler, preheaters, vaporizers, etc.

Thanks for reading.

The post Shell and Tube Heat Exchanger Costing appeared first on ChemEnggHelp.

To start with let us consider a control volume system as shown below.

Control Volume System

In below figure we consider a close volume system. In this system fluid enters at point ‘a’ and leaves at point ‘b’. Also, ‘Ws’ is the work done by system in J/s and ‘Q’ is J/s heat absorbed from surroundings.

So, total energy balance for above system at steady, between the point ‘a’ and ‘b’ will be as below. This we can write using the first law of thermodynamics for control volume system (between point ‘a’ and ‘b’).

(Rate of Accumulation of Energy) = (Rate of Energy inflow) – (Rate of Energy outflow)

In our plants devices such as pumps, compressors, turbines, fans etc. operates at steady state conditions except the time of start up and shut down. These unsteady state conditions are very small duration in comparison with the steady state operation time. So, it is more logical to do the analysis of steady flow to evaluate the performance and design of these devices.

Therefore, we can consider dE/dt = 0, m_a = m_b = m.  Hence, we can rewrite above equation as below:

In above equation ‘Ws’ is the energy added to system (in form of work) in J/s and ‘Q’ is J/s heat absorbed from surroundings. Here, ‘P’ is pressure (pascal), ‘Z’ is height from ground level (m), ‘v’ is volume (m³), ‘u’ is fluid velocity (m/s) & ‘g’ = 9.81 m/s².

Also, ‘α’ is the correction factor in kinetic energy term. For a uniform velocity profile and turbulent flow, α = 1. For laminar flow in a circular pipe with a parabolic velocity profile, α = 2.

Applications of Steady State Flow Processes

• For Compressors & Turbines we can ignore kinetic energy and potential energy terms without appreciable error. Moreover, assuming these devices operating under adiabatic conditions. The above-mentioned control volume steady state energy balance reduces to as below: (i.e., KE = PE = Q = 0)

Note: W_s is positive for turbine & negative for a compressor.

• A nozzle as shown below, we use to increase the flow velocity for the fluid.

So, for this case energy balance for control volume gives:

              u_b² – u_a² = 2*(h_a – h_b) = 2*∆h = 2*C_p*(T_a – T_b)

              For the case when inlet fluid velocity is u_a << u_b, we can rewrite above expression as below:

              u_b = [2*C_p*(T_a – T_b)]^1/2

Mechanical Energy Balance, Bernoulli Equation

In below PFD you can see liquid from a tank is going into the pump suction. From the pump discharge this fluid passes through a heater and then enter into a reactor.

The mechanical energy balance includes kinetic energy, static energy and potential energy. We can write Bernoulli equation between point ‘a’ and ‘b’ without considering friction term as below:

To make above equation more useful for a pumping system as shown in above figure. We require to make two corrections. First is correction for kinetic energy term, which is because of variation in velocity because of position in boundary layer. The second, which is more important is correction for friction losses due to fluid flow and boundary layer formation.

So, below is the corrected Bernoulli equation for incompressible fluids: –

In above equation ‘f’ is the mechanical loss at all points between point ‘a’ & ‘b’ in above figure. Also, in a piping network we use a pump to overcome this friction loss ‘f’. Hence, we can correct above equation for pump work as below:

Now, let us consider one example to see the utility of above equation for the flow of incompressible fluids.

Example for Pumping of DM Water from Tank to Reactor

Let us refer to above PFD for pumping system, pump draws DM Water from the tank through 100NB, Sch-20, SS304 pipeline. The discharge pipeline size is 80NB, Sch-20, SS304. The efficiency of pump is 70% and elevation difference between tank level and reactor inlet is 12 meters. The reactor is operating at atmospheric pressure. Total friction losses between point ‘a’ & ‘b’ is 15 meters.

Average velocity through pump pipe at reactor inlet is 2.5 m/s. Calculate power requirement for the pump & motor size.  

To estimate the power requirement, we will use the below equation:

Various available information in above equation are as follows:

• P_a & P_b are equal to atmospheric pressure (i.e., will cancel out both side)
• (Z_b – Z_a) = 12 meters and g = 9.81 m/s²
• Discharge pipe ID, Db = 84.69mm & Suction pipe ID, Da = 110.08mm
• Pump efficiency, η = 70% and f = 15*9.81 (m/s)²
• Flow is turbulent so, α = 1.0

Discharge velocity, u_b = 2.5 m/s hence u_a = (D_b/D_a)²*u_b = (84.69/110.08)²*2.5 = 1.48 m/s

Flow area of discharge pipe = pi()*(84.69/1000)²/4 = 0.005633 m²

Hence mass flow rate from the pipe line, m = 0.005633*2.5*1000 = 14.083 kg/s

After putting all values in above equation, we get:

ηW_s = 14.083*(12*9.81 + (2.5² – 1.48²)/2 + 15*9.81) = 3737.5 kg-m²/s³

W_s = 3737.5/(70/100) = 5339 Watt

Considering motor efficiency 95% required motor rating will be, E_m = W_s/0.95 = 5339/(0.95*1000) = 5.62 kW

Conclusion

So, in this article first we discussed total energy balance for a control volume system. And, subsequently we saw the application for turbine/compressor and nozzle. After this we worked out with mechanical energy balance or Bernoulli equation for a liquid pump and piping network. Also, we took one example for pumping DM water from the tank to reactor and estimated the power requirement for the pump & motor.

Thanks for your reading.

The post Energy Balance for Steady State Flow appeared first on ChemEnggHelp.